The lubrication system of an engine pressurizes and distributes lubrication fluid, e.g. oil, to the engine lubrication circuits by use of a pump such as a variable displacement vane pump (VDVP). Such a pump typically employs a rotor, a slide and multiple radially extending slidable vanes and cavities which can vary the volume of fluid delivered to the lubrication circuits. The slide is eccentrically offset from the rotor to create pumping chambers defined by the vanes, rotor and inner surface of the slide. A compression spring biases the slide to create large pumping chambers as the default.
When the engine requires less volume of oil or less oil pressure from the pump, a pressure regulator directs oil from the pump output to a regulating chamber in the pump. Pressure in the regulating chamber counteracts the spring biasing force to move the slide into a position which is more closely align the center of the slide with the center of the rotor. As a result, the size of the pumping chambers is reduced. Reducing the pumping chambers reduces the amount of oil drawn into the pump from an oil sump such that the amount of oil output by the pump and the oil pressure are reduced.
Several influence factors come into play with the hydro-mechanical control of the pump displacement as described above. Rotation of the slide about a pivot pin is affected by three forces: the hydraulic forces in the pumping chambers; the slide spring biasing force; and the hydraulic forces in the regulating chamber. The regulating chamber hydraulic force depends on the oil pressure in the regulating chamber, which is controlled by a pilot valve inside an oil control valve. Thus, the regulating hydraulic force is affected by the forces acting on the pilot valve including a pilot valve spring force, a pilot valve hydraulic force and an electrically-generated magnetic force. In addition, the tolerance of a control port in the oil control used for feeding and draining the regulating chamber can also affect control of the pump displacement.
However, further improvements to variable displacement vane pumps and, in particular, oil pressure control of a variable displacement vane pumps with a movable slide for use in engine lubrication systems are desirable. In addition, other improvements, desirable features and characteristics are desirable and will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.